Substrate materials are an essential element in tissue engineering, where the chemical and physical properties of the support matrix can ultimately control the fate and viability of the growing cells.1-4 Bio-materials for applications in regenerative medicine need to offer easy ways to modify and tune these properties in order to control the interactions of the substrate material with the growing tissue. Most materials used for tissue engineering and cell culture present uniform mechanical properties. However, in vivo, cells may find dynamic changes in the stiffness of the extracellular matrix at the interface of different tissues or as a consequence of disease states.5,6 The elasticity of substrate materials creates mechanical cues for the development of the growing cells.1,5,7 
These cues have been widely studied using model systems such as polyacrylamide (Paam) gels, where the stiffness can be controlled by5,6,7,8 adjusting the ratio of reagents during the formulation1,8-10 or performing uneven, or multi-step polymerization of the substrate with different intensities of light or heat.1,3,8,5,11 However, none of these approaches offer a post-synthetic alternative for tuning and controlling the mechanical properties of the substrate. Described herein is a facile method for the photo-patterning of already prepared hydrogel materials to create gradients and interfaces in stiffness and elasticity. By patterning these materials, mechanical cues to control and direct the development of cells can be created.